Fixing non-working WiFi on RT5350

I have a favorite cheap chinese router based on RT5350 (running OpenWRT).

Recently, I was wondering, why I can’t get WiFi on a few of them working. I have one piece running quite old (4xxx svn) OpenWRT where the WiFi works OK. So I tried to compile exactly the same version and install it on the non working piece. I also put the same wifi config there but nothing. It didn’t work.

Then I made a full flash backup from the working device and installed it to the non-working one and WOW! Wifi worked. So I started to compare the freshly compiled image with this backup.

First, I compared installed packages and they were the same versions. Then I tried to compare the whole filesystem with diff.

Solution

Then I realized, that when I was writing bootloader directly to the SPI flash of my device (like in the picture), I’ve had erased the whole chip, so now there are zeroes instead some factory settings like MAC address etc.